textproduct: Albany

WHAT HAS CHANGED

The track of the coastal storm that, in recent days, did not look to bring any precipitation to eastern New York and western New England late Sunday into early Monday, has shifted slightly north. This forced an increase in PoPs for the Sunday night in both spatial coverage and numerical percentage value. For the most part, widespread slight chance PoPs (~15-24%) now exist across the region with a small coverage area of chance (~25-30%) covering portions of the lower Mid-Hudson Valley and northwest Connecticut.

Additionally, temperatures have trended warmer during the prolonged period of unsettled weather for next week. This change owed to the NBM precipitation type solution of snow and a rain/snow mix as opposed to a wintry mix. With the preliminary system in the parade of storms set for next week falling to Wednesday, Day 5 of this forecast period, there is certainly still ample time for this to change. But, given the ensemble majority erring towards warming conditions, it is worth noting that the probability of at least widespread mixed precipitation (freezing rain/sleet) is declining.

KEY MESSAGES

1) Light snow resulting from a coastal storm, whose track is beginning to trend northward, could make for isolated slippery road conditions for the Monday morning commute in portions of the lower Mid-Hudson Valley and northwest Connecticut.

2) Confidence continues to increase in a prolonged period of unsettled weather conditions beginning in the early to middle portion of next week.

DISCUSSION

KEY MESSAGE 1...

In recent days, a coastal storm has been mentioned for its lack of impact on our region due to its track being suppressed southward by the disconnect between its southern stream parent flow and a shortwave embedded in the northern stream that looked to eject out of southeast Canada ahead of it. While impacts are anticipated to be very minimal, it is worth noting that latest guidance has indicated a more northerly track of the coastal storm such that portions of eastern New York and western New England experience resulting light snow showers.

The difference with the latest solutions in comparison to those of days previous has to do with the low that currently lies overhead in central Quebec. This low, along its southeasterly track towards the border of Maine and the Canadian Maritimes, now looks to deepen more significantly, translating to a surface cyclogenesis response by Sunday morning. The persistence of this strengthening trend into Sunday afternoon will result in the slower progression of the aforementioned northern stream shortwave as it traverses Ontario and deepens slightly itself. This solution promotes the phasing of the northern and southern streams as the southern stream upper-low weakens into an open wave Sunday evening simultaneous to the deepening of the wave in the northern stream. The result of this connection would result in deepening the surface cyclone associated with the southern stream, especially as it exits the East Coast near the Carolinas. This connection would also steer the low at least farther northward and potentially closer to the coast depending on the exact phase timing. That said, the farther-northward track of the low would at least increase the probability of precipitation for areas south of the Capital District, particularly portions of the lower Mid-Hudson Valley and northwest Connecticut Sunday night. PoPs were therefore increased for snow showers Sunday night, though remain low at this time, maxing out at slight chance and chance. Depending on timing, this could make the morning commute Monday slippery in isolated places with less than an inch of accumulation expected.

KEY MESSAGE 2...

After a relatively tranquil start to next week, we enter what will likely be a fairly active pattern. Guidance continues to indicate the development of a zonal flow pattern over the Northeast as numerous northern stream shortwaves shunt a broad ridge to the south. A west to east/potentially northwest to southeast baroclinic zone looks to become established across the region beginning Wednesday as a result as a low pressure system deepens in the upper Midwest. Cold air ahead of the boundary followed closely by warm air advection behind it could make for a messy precipitation combination, though the types are highly dependent on the orientation and position of the baroclinic zone.

The latest LREF clusters indicate that ~54% of ensemble members are favoring 500mb heights that are higher than the grand ensemble. Should this be realized, warmer conditions would be expected which would translate to more of a snow and rain/snow mix Wednesday across the region. Should the cooler solution be realized, or the solution favored by ~46% of ensemble members wherein 500mb heights are lower than the grand ensemble, the potential for more of a wintry mix, including freezing rain, increases.

Additional shortwaves and associated surface lows will track through the region towards the end of next week with guidance hinting at additional potential for mixed precipitation. The great deal of uncertainty at this lead time led to our decision to not deviate from the NBM which continues to favor rain and snow or a mix thereof for precipitation type. We will continue to closely monitor trends and make adjustments as lead time decreases.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Through 06z Sunday...While VFR conditions will generally prevail overnight, a disturbance will bring widely scattered snow showers between 06z-10z, which may bring brief periods of MVFR conditions. Due to limited coverage will continue to mention PROB30 at all TAF sites. The -SHSN should end from NW to SE by around 10z. Additional scattered -SHSN may then redevelop at KALB/KGFL/KPSF between 12z-17z due to a weak front moving across the area again with mainly MVFR conditions. The -SHSN will likely be more persistent at KPSF well into the afternoon due to westerly upslope flow, with prevailing MVFR cigs and possible occasionally IFR vsby developing there. Winds will initially be southerly around 5 kt or less, becoming west- northwest this afternoon and increasing to 5-10 kt with gusts around 15 kt at times.

Outlook...

Sunday Night: Low Operational Impact. Slight Chance of SHSN. Washingtons Birthday: No Operational Impact. NO SIG WX. Monday Night: No Operational Impact. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: High Operational Impact. Likely RA...SN. Wednesday Night: Moderate Operational Impact. Likely RA...SN. Thursday: Moderate Operational Impact. Chance of RA...SN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.